(PHP 4, PHP 5)
str_repeat — Wiederholt einen String
Gibt input multiplier mal zurück.
Die zu wiederholende Zeichenkette.
Die Anzahl der Wiederholungen, die auf input angewendet werden sollen.
multiplier muss größer als oder gleich 0 sein. Wenn multiplier den Wert 0 hat, gibt die Funktion einen leeren String zurück.
Gibt die wiederholte Zeichenkette zurück.
Beispiel #1 str_repeat()-Beispiel
<?php
echo str_repeat("-=", 10);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
-=-=-=-=-=-=-=-=-=-=
str_repeat() Function Integer Overflow
For more info see : 
http://bugs.php.net/bug.php?id=51105
Here is a simple one liner to repeat a string multiple times with a separator:
<?php
implode($separator, array_fill(0, $multiplier, $input));
?>
Example script:
<?php
// How I like to repeat a string using standard PHP functions
$input = 'bar';
$multiplier = 5;
$separator = ',';
print implode($separator, array_fill(0, $multiplier, $input));
print "\n";
// Say, this comes in handy with count() on an array that we want to use in an
// SQL query such as 'WHERE foo IN (...)'
$args = array('1', '2', '3');
print implode(',', array_fill(0, count($args), '?'));
print "\n";
?>
Example Output:
bar,bar,bar,bar,bar
?,?,?
Here is a shorter version of Kees van Dieren's function below, which is moreover compatible with the syntax of str_repeat:
<?php
function str_repeat_extended($input, $multiplier, $separator='')
{
    return $multiplier==0 ? '' : str_repeat($input.$separator, $multiplier-1).$input;
}
?>
Needed a function to repeat a string with a separator.
<?php
/**
 * Repeats <tt>$string</tt> <tt>$multiplier</tt> times, separated with <tt>$sep</tt>.
 *
 * str_repeat_sep('?', ',', 3) ==> "?,?,?"
 * str_repeat_seap('..', '/', 3) ==> "../../.."
 *
 * @param string $string
 * @param string $sep
 * @param int $multiplier
 * @return string
 */
function str_repeat_sep($string, $sep, $multiplier) {
  $ret = "";
  for($i=0;$i<$multiplier;$i++) {
    if ($i) $ret.=$sep;
    $ret.=$string;
  }
  return $ret;
}
?>
If you want to hide a part of your password, you can use this code. It's very simple and might be required in your user management panel.
<?php
$password = "12345abcdef";
$visibleLength = 4; // 4 chars from the beginning
echo substr($password,0,4).str_repeat("*", (strlen($password)-$visibleLength));
?>
In reply to what Roland Knall wrote:
It is much simpler to use printf() or sprintf() for leading zeros.
<?php
   printf("%05d<br>\n",  1); // Will echo 00001
   sprintf("%05d<br>\n",  1); // Will return 00001
?>
str_repeat does not repeat symbol with code 0 on some (maybe all?) systems (tested on PHP Version 4.3.2 , FreeBSD 4.8-STABLE i386 ).
Use <pre>
while(strlen($str) < $desired) $str .= chr(0);
</pre> to have string filled with zero-symbols.
Note that the first argument is parsed only once, so it's impossible to do things like this:
echo str_repeat(++$i, 10);
The example will produce 10 times the value of $i+1, and will not do a cycle from $i to $i+10.
(For the benefit of those searching the website:)
This is the equivalent of Perl's "x" (repetition) operator, for eg.  str_repeat("blah", 8) in PHP does the same thing as "blah" x 8 in Perl.